Part A
Urinary incontinence is a widespread problem in the United States and throughout the world. Urinary incontinence affects people of all ages and can severely impact a patient both physiologically and psychologically.
In approximately 30% of the women suffering from urinary incontinence, incontinence is caused by intrinsic sphincter deficiency (ISD), a condition in which the valves of the urethral sphincter do not properly coapt. In approximately another 30% of incontinent women, incontinence is caused by hypermobility, a condition in which the muscles around the bladder relax, causing the bladder neck and proximal urethra to rotate and descend in response to increases in intraabdominal pressure.
Hypermobility may be the result of pregnancy or other conditions which weaken the muscles. In an additional group of women with urinary incontinence, the condition is caused by a combination of ISD and hypermobility.
In addition to the conditions described above, urinary incontinence has a number of other causes, including birth defects, disease, injury, aging, and urinary tract infection.
Numerous approaches for treating urinary incontinence are available. For example, several procedures for stabilizing and/or slightly compressing the urethra so as to prevent the leakage of urine have been developed. The stabilizing or compressive force may be applied directly by sutures passing through the soft tissue surrounding the urethra or, alternatively, may be applied by means of a sling located under the urethra and suspended by sutures. The sutures may be anchored to the pubic bone by means of bone anchors or, alternatively, the sutures may be attached to other structures such as fascia.
A device for dissecting around a tubular structure such as the urethra or the bladder neck is available from Lone Star Medical Products. The Lone Star device has two shafts which can be positioned in the tissue between the urethra and the vaginal wall using cystoscopy, vaginal or rectal examination, or an examination of the position of the instrument around the urethra with the bladder opened. The two shafts can be locked together to pinch the intervening tissue. A sharp blade is inserted into one of the shafts and advanced into the second shaft, cutting the tissue in between the two shafts. The cut in the tissue can be expanded using a right angle clamp and an artificial sphincter guided by a suture attached to the cutting blade of the device can be introduced into the expanded cut.
With the Lone Star device, the distance between the two shafts cannot be gradually adjusted. In addition, the ends of the shafts of the Lone Star device come in direct contact with the tissue or bone while being advanced towards the tissue between the urethra and the upper vaginal wall. The shafts of the Lone Star device are flat at their distal ends.
Thus, there is a need for devices which simplify treatments for urinary incontinence and increase their safety. Sling application devices for treating urinary incontinence which reduce the risk of inadvertent pinching of the urethra and undesirable scoring of tissue or bone during advancement of the device would be particularly desirable. It is also desirable to have a sling application device that does not employ a guiding suture and can create or maintain an opening in the tissue between the urethra and the upper vaginal wall without the use of a right angle clamp, thereby simplifying the procedure.
U.S. Pat. No. 5,611,515, issued Mar. 18, 1997 to Benderev et al., introduces pioneering minimally invasive percutaneous and transvaginal bladder neck stabilization approaches. The percutaneous approach of Benderev et al. involves stabilizing the bladder neck using a bone anchor which is percutaneously introduced from the abdominal side of the patient. The transvaginal approach of Benderev et al. involves stabilizing the bladder neck using a staple or bone anchor which is transvaginally placed into the pubic bone. There is also a need for further devices and methods for improving or maintaining urinary continence involving stabilization or compression of the bladder neck or urethra, particularly devices and methods of the present invention that are less invasive than many of those currently available.
Part B
The present invention relates to the treatment of stress urinary incontinence “SUI,” and to improved methods and surgical devices for the surgical treatment of SUI. The devices disclosed herein are additionally useful in a wide variety of other surgical procedures.
Genuine stress incontinence is the involuntary loss of urine due to a sudden rise in intraabdominal pressure. It has been estimated that between 40% and 50% of young, healthy nulliparous women admit to occasional mild stress incontinence; however, at least 80% of stress incontinence patients are in the perimenopausal age group and are multiparous. Raz has suggested that the female urethral continence mechanism is dependent on the interaction of four urethral factors: urethral closing pressure, urethral length, urethrotrigonal anatomy, and urethral reception of intraabdominal pressure. Raz, S., Modified bladder neck suspension for female stress incontinence, Urology, 17:82, 1981.
The urethral closing pressure is predominantly a result of the interaction of smooth and striated muscle sphincter activity, but there is also some contribution by nonmuscular urethral factors such as the submucosal vascular plexus, the elastin and collagen content of the urethral tissues, and a sphincter like effect of the mucosa. There has been considerable diversity of opinion regarding the anatomic structure and the innervation of the urethral sphincters, and a variety of views have been expressed in the literature.
Urethral length is important in the maintenance of continence. However, although it certainly interacts with other factors to contribute to continence, a short urethra alone will not produce incontinence. Urethral length varies considerably in normal women, and women with proven genuine stress urinary incontinence do not invariably have urethral shortening.
Urethrotrigonal anatomy, which can be demonstrated by lateral cystourethrography, should fulfill certain criteria. The bladder base should lie above the level of the inferior ramus of the symphysis, and with straining should not descend more than 1.5 cm. There should be a normal urethrotrigonal alignment with an angle normally less than 100 degrees, and the urethral axis should be approximately 35 degrees from the vertical. In the hypermobile situation loss of all of the normal anatomic features may occur, a radiologic finding that correlates with the clinical finding of cystourethrocele. However, clinical experience has shown that the coexistence of cystourethrocele and incontinence does not predict that the incontinence is of a genuine stress variety.
The transmission of intra-abdominal pressure to the intra-abdominal portion of the proximal urethra is also reported to be important in the maintenance of continence. This is a passive phenomenon, and is the result of the normal anatomic configuration just described. Whenever there is a rise in intra-abdominal pressure during such stresses as coughing or straining, the pressure is transmitted not only to the bladder but also to the proximal urethra, with resultant increase in the closing pressure, and prevention of leakage. If the urethral axis is altered, rotational descent will drop the proximal urethra and bladder base from its intra-abdominal location, and will obviously impair such pressure transmission.
A wide variety of operations have been used to correct this condition, generally involving the principles of elevating the bladder neck anteriorly and/or elongating and narrowing the proximal urethra. Two of the most popular operations today for stress incontinence are the Marshall-Marchetti-Krantz and Birch vesicourethropexies. The Marshall-Marchetti-Krantz technique has at least an eighty-five percent success rate, against which other operative success rates must be measured. Recently, the Pereyra operation and its modifications have enjoyed some popularity, but less than basic techniques.
Notwithstanding the foregoing, however, there remains a need for an improved treatment for SUI. Preferably, the treatment is as noninvasive as possible under the circumstances, and will eliminate or minimize hospitalization and the use of general anesthetics. In addition, there remains a need for improved medical instrumentation such as tissue cavity dilators, incision guides, bone-piercing guide drivers, and quick-connect slings and suture-securing devices for use in connection with SUI treatment and other medical procedures. U.S. patent application Ser. No. 08/042,739, entitled “Bladder Neck Suspension Procedure”, filed Apr. 5, 1993 by Benderev et al., now issued U.S. Pat. No. 5,611,515, introduces pioneering minimally invasive percutaneous and transvaginal bladder neck stabilization approaches. The percutaneous approach of Benderev et al. involves stabilizing the bladder neck using a bone anchor which is percutaneously introduced from the abdominal side of the patient. The transvaginal approach of Benderev et al. involves stabilizing the bladder neck using a staple or bone anchor which is transvaginally placed into the pubic bone. The methods and devices of the present invention may be used in several urethral or bladder neck stabilization procedures that are less invasive than many of those currently available.